Earth's Structure Vocabulary Terms

Here is an Earth science vocabulary list of key terms for learning about Earth's structure.

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Earth's Structure Vocabulary

Asthenosphere: the soft, flexible upper layer of the mantle, on which the tectonic plates move.

Atmosphere: the gaseous layer that surrounds Earth.

Basalt: a dark, dense igneous rock with a fine texture, found in oceanic crust

Biosphere: living organisms and their habitats

Continental crust: the crust that comprises Earth's continents. It is composed mainly of granitic rock, and it is less dense and thicker than oceanic crust, with an average density of 2.7 g/cm3, and an average thickness ranging from 30 to 70 km (20 to 45 miles). Continental crust is much older than oceanic crust, with some rocks estimated to be over 3.8 billion years old.

Core: the layer at the center of the Earth, below the mantle. The core makes up about 33% of Earth's mass, and has a radius of 3,480 km (2,162 miles).

Crust: the thin layer of rock that forms Earth's outermost layer. The crust makes up only about 1% of Earth's mass, and is 5 to 100 km (3 to 60 miles) thick.

Hydrosphere: the part of Earth that is composed of water, including oceans, lakes, rivers, glaciers and polar ice caps. Clouds, rain and snow are also part of the hydrosphere.

Inner core: a dense sphere of solid iron and nickel in the center of the Earth. It is the hottest part of Earth, with temperatures ranging from 4,000 to 6,000 degrees C (7,000 to 11,000 degrees F) and an average density of 15 g/cm3. Despite the high temperature, the inner core is solid due to the immense pressure at Earth's center.

Lithosphere: a rigid layer made up of the crust and uppermost part of the mantle.

Mantle: the layer of hot, solid material between Earth's crust and core. It makes up 67% of Earth's total mass, and is 2,900 km (1,800 miles) thick.

Mesosphere: the solid lower layer of the mantle located below the asthenosphere.

Oceanic crust: the crust that is found on the ocean floor. It is composed mainly of basaltic rock, and is denser and thinner than continental crust, with an average density of 3 g/cm3, and a thickness ranging from 6 to 11 km (4 to 7 miles). Oceanic crust is younger than continental crust, because it is constantly being remade at the mid-ocean ridges. The age of oceanic crust does not exceed 200,000 years.

Outer core: a layer of molten iron and nickel that surrounds the inner core of Earth.

Tectonic plates: large pieces of the lithosphere that slowly move on top of the asthenosphere. There are 7 primary and numerous smaller tectonic plates.